1. Field
The embodiments described below relate generally to delivery of radiotherapy treatment. More specifically, some embodiments are directed to rotational radiation treatment of moving patient areas and systems for delivering such treatments.
2. Description
Radiotherapy or radiation therapy is used to treat cancer and other diseases with ionizing radiation. Conventional radiotherapy systems generate and direct a beam of radiation to a targeted treatment area within a patient volume. The radiation beam is intended to injure or destroy cells within the targeted area by causing ionizations within the cells or other radiation-induced cell damage.
Radiotherapy treatment plans for delivering radiation to a patient are intended to maximize radiation delivered to a targeted area, while minimizing the radiation delivered to healthy tissue. In this regard, the treatment of a moving target area poses a challenge to radiotherapy. In the context of rotational radiotherapy treatments, the treatment of moving targets is further complicated due to the movement of the gantry in one or more arcs around the patient. Such rotational radiotherapies include but are not limited to Arc-Modulated ConeBeam Therapy, Intensity Modulated Arc Therapy, and a variety of other radiotherapy treatment schemes that involve rotating a linear accelerator (LINAC) gantry about the patient and delivering radiation to a targeted patient area from a number of different gantry angles. In some contexts, the delivery of the treatment radiation may be either continuous or at discrete locations.
One conventional method for addressing the delivery of radiation treatment to moving targets includes using an increased margin of delivery around a target that is large enough to account for target excursions from a nominal position. While the increased margin may result in the target receiving a desired radiation dose, surrounding healthy tissue or organs are at an increased risk of also receiving radiation. Gated treatment techniques to address moving targets involve determining a gating window during which the target movement is minimized to deliver the radiation treatment. For example, radiation may be delivered to the target only when the patient is within 80% exhalation of the breathing cycle, a period when motion of the targeted treatment area may be relatively motionless. However, acquisition of planning images (e.g., 4D CT computed tomography) and a breathing monitoring device to provide an indication of the phases of the patient's breathing cycle are needed for this technique. One proposed technique for delivering radiation to a moving target involves using an auxiliary device to determine the location and the shape of the target at any point in time and reshaping the MLC (multileaf collimator) leaves of the radiotherapy system to follow (i.e., track) the target shape at any point in time. However, this technique also requires an auxiliary device in addition to the radiotherapy system.
The present inventors have realized that conventional rotational radiation treatments are inefficient and insufficient for rotational radiotherapy treatment of moving targets. Accordingly, other methods and systems to provide rotational radiation treatment of moving target areas are desired.